The Bieber Factor: What Makes Voices Unique

Below:

Next story in Science

Justin Bieber, Usher and others have unique sounding voices, in
part, because their relatives over the ages lived within large
social groups, suggests a new study.

The study, published in the latest issue of Current
Biology, is among the first to empirically demonstrate that
the size of an animal's social group helps to determine the
uniqueness of that individual's voice. The results could also
explain why everyone looks, sounds, and even smells so different.

"Imagine if you hung out with the same three people every day,"
added Pollard, a researcher in the Department of Ecology and
Evolutionary Biology at the University of California, Los
Angeles. "You certainly wouldn't need to dress like Lady Gaga to
be recognized, but in a group of 50, 100, or more, it sure could
help."

For the study, Pollard and colleague Daniel Blumstein examined
eight different species of rodents that live in social groups of
different sizes and complexities. The rodents included California
ground squirrels, Olympic marmots, yellow-bellied marmots,
black-tailed prairie dogs, white-tailed prairie dogs,
thirteen-lined ground squirrels, Belding's ground squirrels, and
Richardson's ground squirrels.

The researchers caught individuals from each of these groups in a
live trap. Since the rodents are afraid of humans, they often
emit vocal alarm calls whenever a person approaches. The
researchers recorded these calls and compared them to the alarm
vocalizations of other members in that rodent's particular social
group. Pollard explained that the social groups could include
both relatives and members that aren't so closely related.

Social group complexity did not predict the uniqueness of each
voice, but the size of the groups did. The larger the social
group, the more distinctive the voices were.

"Differences in rodent voices are much like differences in human
voices," explained Pollard. "Some animals' voices are
high-pitched, others are low. Some voices are clear, others are
more scratchy. Individual animals also have different timbre and
use different patterns of emphasis. Each call has an animal's
unique vocal stamp on it."

The researchers believe the findings likely apply to all social
animals where recognizing individuals is critical. These include
social rodents, dolphins, whales, elephants, horses, social
carnivores (such as wolves and hyenas), and primates -- including
humans.

"You can think of it as a Where's Waldo problem," Pollard said.
"Finding any particular individual in a crowd is tough, and the
bigger the crowd, the tougher it is. There are more distracters
to sift through, and if individual uniqueness is low, that means
more doppelgangers, more cases of mistaken identity."

The solution, she believes, is to make each individual more
unique.

"It's the equivalent of giving everyone a crazy sweater with a
different colorful pattern on it," she said.

The clothing analogy might not be too far off, since the human
population boom, combined with ever more crowded conditions, is
likely increasing evolutionary pressure on our own individuality.
Distinctive clothing, piercings, tattoos and other unique
identifiers are perhaps an effort to literally stand out from the
crowd.

Michael Beecher, a professor of psychology and biology at the
University of Washington, developed the hypothesis in the 1980's
that social group size predicts individual differences. He told
Discovery News that this new paper "is the first really complete
test of the hypothesis with a large number of closely-related
species."

"People often assume that our ability to recognize individuals is
simply a consequence of natural biological variability in
detectable physical traits found in any population of individuals
in any species," Beecher said. "If this were true, it should be
equally easy to distinguish among individuals of any species, so
long as you have the requisite perceptual abilities of that
species."

According to the researchers, however, larger social groups make
it more difficult to identify members, prompting the evolutionary
drive for individual uniqueness.